1. Field of the Invention
This invention relates to a warning circuit in a flashlight device using an auto-controlled speed light and a camera.
2. Description of the Prior Art
The variation in the quantity of light emitted by the auto-controlled speed light has an upper and a lower limit. Therefore, depending chiefly on the selected aperture value and the selected distance to the object to be photographed, over or under exposure may occur. For this reason, a warning device has heretofore been proposed which displays, by means of a meter needle, the relation between the aperture value and the object distance exceeding the upper and the lower limit of the quantity of light emitted and the sensitivity of the film loaded in the camera, thereby calling attention to changing the aperture value and the object distance, thus preventing a failure in exposure.
However, in case of flashlight photography in the dark, the meter needle cannot be seen and this is inconvenient as the means of warning. Also, in order for the film sensitivity to be electrically introduced in the device, it is necessary to deviate the interlocking positional relation between a variable resistor interlocking with the aperture mechanism to introduce the aperture value in the device, and the aperture mechanism in accordance with the film sensitivity, and this makes the device more complex in construction.
It is an object of the present invention to provide a warning device in an auto-controlled speed light which displays by means of a light-emitting element such as a light-emitting diode whether the combination of the aperture value, the object distance and the film sensitivity is within the range of the upper and lower limits of the quantity of light emitted by the auto-controlled speed light.
There has heretofore been a device which introduces exposure information such as the aperture value of the photographic lens and the object distance from a camera or a lens into a speed light and displays in advance without resorting to light emission whether the light controlling operation of the speed light is properly effected in accordance with said information. The display effected by the display device when such a speed light is used in combination with a camera or a lens which does not generate the information such as the film sensitivity, the aperture value of the lens and the object distance has been coincident with the display of the fact that the light controlling operation is not properly effected, and this has been undesirable for the observation. That is, the observer cannot distinguish between these two displays.